I too consider myself something of an amateur historian, and would be most delighted if historically (and monetarily) valuable items such as those mentioned in your letter were found. However I fear it may be too late. Some years ago, when my dwelling was being constructed, several items were encountered during excavations for the installation of a septic tank. These included maps, a diary with the name 'de Vlamingh', and 2 boxes which could not be opened. Believing them to be worthless debris left by the previous owner, Cecil B. de Vlamingh (a junk and scrap dealer), we threw them out. If despite this you still wish to excavate, then please contact me to begin detailed negotiations. Your crew and their wives (and your own self and your most lovely wife) are also welcome to take up residence here, once again subject to certain conditions including 'jus primae noctis' style rights for me and my housemates Steve and Cyrix.
Looking forward to your response.